I suspect this would require advanced MMA skills, but it would be very useful if one could modify the front end so that any MMA defined function calls in a Compile[] could be flagged if they are not compilable, because uncompilable functions would cause slow compiled code through calls to MainEvaluate[].

Question 1096 shows how to get lists of compilable functions.

How might the functions in a Compile[] definition be dynamically checked against such a list (i.e. as the user types them) and highlighted in some way if they are/are not compilable?

(I have not yet got around to calling a compiled function from a compiled function, but the obvious next step would be to maintain a secondary list of user defined functions that can be called in a Compile[] and to provide similar highlighting.

Would someone exceedingly smart be able to see how to do both these things?)


It has been pointed out in comments and through a linked question, whose significant content I have quoted, that "compilable?" is not a simple question to answer. I would therefore like to amend the question as follows:

How could one customize the front-end (so that feedback is immediate on typing) so that MMA defined functions that are not listed as compilable (whether conditionally or not) are highlighted if used inside a Compile[]?

Rationale: one cannot easily say a function is compilable, but given that there are lists of MMA functions that may be compilable, any function not on that list may be assumed non-compilable and the sooner one can see that the less effort one is likely to waste writing a function for compilation that, ultimately, cannot compile. [The other suggestions may then be incorporated to ease the process of determining whether compilation then actually succeeded without calls to MainEvaluate]

  • $\begingroup$ I don't insist, I just didn't know there might be other options; I do however want the feedback to be immediate so I don't spend time building a complete definition only to find it is inappropriate (I am using CompiledFunctionTools`CompilePrint[] at the moment to do precisely that), and I am tired of scanning the lists with Mk I eyeball. $\endgroup$ Oct 12, 2016 at 12:18
  • $\begingroup$ Perhaps SetSystemOptions["CompileOptions" -> "CompileReportExternal" -> True] would be somewhat helpful. $\endgroup$
    – Michael E2
    Oct 12, 2016 at 13:02
  • $\begingroup$ @MichaelE2 That's an interesting additional tool, thanks; the linked question also gives the quote "It (compiling) is not as simple as just a list of functions. For a number of functions, some uses of the function are supported and others are not. Thus, the list of functions is a starting point, but does not give the whole story." Hmmmm. $\endgroup$ Oct 12, 2016 at 13:09
  • 2
    $\begingroup$ Are you aware that the answer to "Is f compilable?" is usually not a simple yes/no? There are often restrictions on the compilable syntax, sometimes very narrow restrictions. $\endgroup$
    – Szabolcs
    Oct 12, 2016 at 15:55
  • $\begingroup$ The function FastCompiledFunctionQ in (24595 ) is a perhaps more efficient version of Julien's CompileEx. $\endgroup$
    – Michael E2
    Oct 12, 2016 at 15:56

2 Answers 2


One idea is to use the AutoStyleWords option of cells to color selected words. For example, the following stylesheet colors all words given by Compile`CompilerFunctions the color RGBColor[.3, .5, .5] indicating that they are acceptable compiler functions, and other words will remain black, indicating that they are probably not compiler functions:

    StyleDefinitions -> Notebook[
        Cell[StyleData["CompileInput", StyleDefinitions->StyleData["Input"]],
        Cell[StyleData["CompiledFunction"], FontColor->RGBColor[.3,.5,.5]]

Then, here's an example of a compiled function using the "CompileInput" style:

enter image description here

You can see that IntegerQ and MatchQ have been flagged as noncompilable functions.

  • $\begingroup$ Thanks, I'm still naive about StyleDefinitions stuff so will need to digest this and mod so that I can put it in my own named stylesheets. Puzzled by the fact that I have to manually apply the CompileInput style to see the result as shown above; I must be misunderstanding how it works - to me it looks as though Input is modified as well (my ignorance)...But it does do exactly what I wanted, thank you - accepting on that basis. $\endgroup$ Jun 16, 2019 at 8:34

Okay so this is not an answer (it's to big to write a comment for) to your exact question but a dirty workaround. But it works.

We can write a simple wrapper for Compile which warns us if we get MainEvaluates and Prints them.

If[Length[meCases]>0,Print[ToString[Length[meCases]]<>" MainEvaluates detected.\n\n"<>StringJoin[Riffle[meCases,"\n\n"]]]];

This does only printing but its easy to let it throw an error or something you would prefer.

A Testrun:


2 MainEvaluates detected.

Function[{i}, MatchQ[i, _?OddQ]][ R0]

Function[{i}, MatchQ[i, _?IntegerQ]][ R0]


You can save the definition of CompileEx to a package and load it or save it in the kernel/init.m to have it always by you.

I know its not the best solution but hey, better than nothing. But i'm sure, someone here is able to tweek the FrontEnd to do what you want.

  • $\begingroup$ That's also useful, thank you - even though it doesn't do the dynamic parsing it would save a bit of manual checking. $\endgroup$ Oct 12, 2016 at 13:11

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